The present invention relates to a pinch valve used in a fluid transport pipeline in various industrial fields, such as chemical factories, semiconductor production, food processing, biotechnology or the like, and, more particularly, to a pinch valve which is compact and mitigates the damage of a tube body suffered during the opening and the closing of the valve.
Hitherto, various pinch valves have been proposed, and an example is disclosed in Japanese Examined Utility Model Publication No. 45-3264. According to this publication, as shown in FIGS. 11 and 12, in two upper and lower pistons 51, 52 fitted in a cylinder 50 on a leg member 49 constituted by a leg stand 47 and leg rods 48, the upper piston 51 is fixed to the upper end of a shaft rod 53 and the lower piston 52 is fixed to the upper end of a pipe shaft 54 loosely fitted on the shaft rod 53. On the lower portion of the pipe shaft 54 is provided a wing piece 55 which is fixed to a lower pressing piece 57 via connecting bars 56. On the other hand, an upper pressing piece 58 is fixed to the lower end of the shaft rod 53. Also, the center portion of a valve tube body 61 supported by the leg member 49 and two lateral rods 60 spanned between flanges 59 fitted on both ends of the valve tube body 61 is pressed by the upper and lower pressing pieces 58, 57, then the upper and lower pressing pieces 58, 57 connected to the pistons 51, 52 are symmetrically moved up and down by suitably forcing pressurized air into holes 62, 63, 64 pierced in the cylinder 50, so that the valve tube body 61 is opened and closed.
Now, at present, in an apparatus for manufacturing semiconductors in which various pipelines and control devices are arranged and complicated pipeline design is performed, allowing the apparatus per se to be compact has been required. As a result, a pinch valve used in the pipeline of the apparatus must be compact in order to save a space, and thus making the pinch valve compact in the apparatus is an important problem. Also, a pinch valve able to regulate a very small flow rate is required.
However, in the pinch valve described above, since the drive and the valve body are constituted as separate components, and the leg member 49, the leg stand 47 and the wing piece 55 are provided between the cylinder 50 and the valve tube body 61 which is a flow passage, the whole height of the valve is very large and thus the valve cannot be made compact. Consequently, the above pinch valve cannot be used as a pinch valve in the pipeline of the semiconductor manufacturing apparatus. Also, since, in such construction of the pinch valve, it is difficult to optionally adjust an opening degree of the valve tube body 61, the adjustment of a very small amount of flow rate cannot be performed.
The present invention has been conceived in view of the problems of the prior art as stated above and the purpose of this invention is to provide a pinch valve the whole height of which is low in comparison with the conventional pinch valve, which is compact and which remarkably mitigates the damage of the tube body suffered during the opening and the closing of the valve, and which is able to adjust a very small flow rate.
In order to achieve the above purpose, the constitution of the present invention is characterized in that it comprises a body containing an elastic tube body constituting a flow passage for a fluid, a cylinder body joined to the upper portion of the body at the lower end of the cylinder body and having a first cylinder portion at the upper portion of the interior of the cylinder body and a second cylinder portion having a diameter larger than that of the first cylinder portion at the lower portion of the interior of the cylinder body, a first piston sliding up and down on the inner periphery of the first cylinder portion, and a second piston sliding up and down on the inner periphery of the second cylinder portion, the first piston being provided with a first interlocking rod suspending from the center of the lower surface of the first piston, passing through the second piston and having a first pressing piece at the lower end of the first interlocking rod, the second piston being provided with second interlocking rods suspending from both ends of the lower surface of the second piston, passing through the first pressing piece and having a second pressing piece at the lower ends of the second interlocking rods, the first and second pressing pieces are arranged to clip the elastic tube body from the upper and lower sides, a spring elastic body urging the first pressing piece being arranged between the second piston and the first pressing piece, and an opening communicating with a space enclosed by the lower end surface of the first piston, the upper end surface of the second piston and the inner peripheral surface of the cylinder body being provided in the cylinder body.
In a preferred embodiment of the present invention, a pair of couplings are connected to both ends of the tube body, and a pair of cutouts receiving the pair of couplings are provided on the lower end portion of the cylinder body in the direction of the flow passage.
Also, the body is provided with a groove receiving the tube body and the couplings and with guide slots in which the second pressing piece is fitted to move up and down, at the location perpendicularly intersecting the groove. Further, the first pressing piece is provided with first through-holes through which the second interlocking rods penetrate at the symmetrical locations in relation to the axis of the flow passage, and the second piston is provided at the center portion thereof with a second through-hole on which the first interlocking rod slides in a sealing manner.
Also, in another embodiment, the upper surface of the cylinder body is provided with an opening portion, the upper portion of the first piston is integrally provided with a projecting male screw portion penetrating the opening portion of the cylinder body for adjusting the opening degree of the tube body, and a stopper pressed on and separated from the upper surface of the cylinder body and a lock-nut pressed on the upper surface of the stopper are rotatably screwed with the male screw portion for adjusting the opening degree of the tube body.
In addition, according to a further embodiment, the outer peripheral surface of the tube body is provided with a protecting portion.
Also, the dimension of the first pressing piece in the direction perpendicularly intersecting the axis of the flow passage is larger than that of the guide slot.
Further, the material of the tube body is EPDM, fluororubber, silicone rubber or a composition of these materials.
More preferably, the tube body is composed of a composition of tetrafluoroethylene and rubber elastic body.
Also, although the cylinder body, the opening degree adjusting male screw portion, the stopper, the lock nut and the body can be made of a material having rigidity, such as metal or plastic, and thus the materials of those components are not especially limited, a plastic such as PVC, PVDF or PFA is particularly preferable.